I record MP4 on my GH4 because I use Windows computer –
ProRes is best for MAC !
Have you tried to make Proxy’s in Vegas ?
Creating Proxy Files in Vegas Pro
1. Add your clips to the Project Media window.
2. Right-click the clips in the Project Media window and choose Create Video Proxy from the shortcut menu.
Vegas Pro creates video proxy files (.sfvp0) alongside the original files in Windows Explorer. You will not see these files in the Project Media window or Vegas Pro Explorer.
4. Add your clips to the timeline and edit your project as usual.
The Preview Quality setting in the Video Preview window determines whether the proxy files or original files are used for editing and preview:
When the preview quality is set to Draft or Preview, the proxy file is used.
When the preview quality is set to Good or Best, the original file is used.